Coffee oils must be fully emulsified to give you the freshest, most flavorful cup of coffee.
Oil and water do not mix -- unless there is an agent to hold them in a stable suspension. That is what an emulsifier does. Think of vinegar and oil salad dressing. You have to shake it first. With an effective emulsifier, it would keep in the shaken-up state. The flavor of coffee is created by the release of aromatic oils within the coffee bean in the roasting process, which, properly emulsified, give you a fresh, flavorful cup of coffee.
Roasting
You do not need to add any emulsifiers at all to roasted coffee beans. The fats, sugars and starches released from the bean during the roasting process are the emulsifiers. The problem is that the oils and starches that are released in roasting begin to degrade rapidly under the twin assaults of moisture and oxygen. Within a week after roasting, coffee will taste stale unless you protect the grounds. You can slow the degradation process, but you cannot stop it. The age of the beans is of little account. The degradation process begins from the time of roasting.
Vacuum Seal
Always air-cool grounds if you grind and roast them yourself. You can protect fresh coffee grounds from the assault of oxygen by storing them in vacuum-sealed packs. It is best to use several small packs and grind fresh beans every few weeks. The oils, starches, fats and sugars of the bean begin a chemical reaction after roasting that decays the flavor of the coffee. Optimum handling delays the process, but once it is complete, the coffee will simply taste stale, regardless of well emulsified it is.
Storage
Keep the vacuum-sealed bags of coffee grounds in either a cool, dry spot or a freezer to protect them from the effects of moisture. This is also why you should always air-cool fresh roasted beans rather than rinsing them. Any moisture that touches the grounds before brewing will speed up the degradation process.
Additives
If you like your coffee black, you need not worry about how well additives are emulsified. While sugar naturally dissolves into the coffee, powdered creamers have oils that, if not properly emulsified, will clump up or feather in your cup. Different dry creamers use different emulsifiers and remain fresh for different lengths of time. If a powdered creamer clumps or releases puddles of oily residue at the top of the cup, choose another brand of creamer. But an oily residue at the top of the cup after adding a powdered creamer can also be a sign that the coffee has gone stale and can no longer emulsify both the coffee oil and the additive.
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